


Reproductive Drive

by ros3bud009



Category: Transformers - All Media Types, Transformers: Prime
Genre: Breeding, Breeding Kink, Established Relationship, Fluff, M/M, Mating Cycles/In Heat, Sappy as fuck, Spark Sexual Interfacing, Sticky Sexual Interfacing, Technically dub-con (more details in note), Unconfirmed Mech Preg
Language: English
Status: Completed
Published: 2017-05-27
Updated: 2017-05-27
Packaged: 2018-11-05 11:19:51
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,150
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11012385
Author URL: https://archiveofourown.org/users/ros3bud009/pseuds/ros3bud009
Summary: Fill for the prompt: Optimus Prime pinning down his partner, rawing them hard, all the while telling them how much he is enjoying putting a baby in them"A sudden warning popped up on Ratchet’s HUD about detecting heat pheromones, and Optimus’s optics brightened before the medic’s own as he bent his helm down closer to Ratchet’s.'I will want to fill you with our child, Ratchet.'"





	Reproductive Drive

**Author's Note:**

> This fic was meant as a fill for this prompt on maccadams-filthy-fills on tumblr:
> 
> "Optimus Prime pinning down his partner, rawing them hard, all the while telling them how much he is enjoying putting a baby in them"
> 
> I got derailed by fluff and sap but hopefully it still fits the bill.
> 
> Also, I tagged as dub-con to be safe because of the inherent dubiousness involved when heat is used in a fic. As well, a pretty important decision re: pregnancy is made during interfacing brought on by heat. However, OP and Ratchet are a long established couple in this fic and nobody is coercing the other, so the dubiousness is minimal. However, I don't want anyone going in not knowing.
> 
> Also also, I use the term forge where usually folks use gestational tank/chamber.

“I’m going into heat.”

Ratchet had already been midway through scanning his Prime when Optimus laid his servo on his arm and spoke.

Normally, the medic would have gone ahead with the scan anyway when Optimus opposed. It wouldn’t have been the first time that Optimus had dismissed the need for Ratchet’s concern when he did, indeed, need it.

But Optimus would never flat out lie to Ratchet. Not about something like this.

And the way his optics had been overly bright and his armor flared to release the unusually high temperature of his systems, not the mention the awkwardness in the normally poised Prime’s voice when he had asked if Ratchet had a moment to speak in private—

Ratchet canceled the scan and folded it away.

“You’re certain?”

“Unfortunately so,” Optimus admitted, his lips curled with chagrin. “I would guess it will fully set in within the next day.”

Ratchet sighed, scrubbing his face as he leaned his hips back against his work station. It hadn’t been a conscious choice, but it did calm his spark some to put even that amount of space between them. Not that it didn’t still long, but Ratchet knew how to keep himself composed during Optimus’s heats.

“And your heat cycles are regular enough that I don’t doubt it. At least that will give us just enough time to switch around shifts and duties to cover for your absence.”

“I–” Optimus stopped himself, and in the shortest of moments, his optics flared and tracked down Ratchet’s frame.

Ratchet suddenly felt his own systems start to kick into high gear despite the shame that followed. It didn’t mean anything significant. While Optimus wasn’t fully in his heat yet, the lead up still meant his interface protocols were primed and ready to act. It was only natural those protocols would react to his lover’s presence – but Optimus was no slave to his protocols.

And indeed, Optimus was quick to refocus again, his optics fixed on Ratchet’s face, his voicebox audibly rebooting. “Given the circumstances, I don’t know that I have the luxury to address it on my own as I have before.”

Ratchet crossed his arms in a desperate bid to close himself off as his spark reeled in his chest.

“I admit, we are a very small team,” Ratchet replied, hoping against hope that his voice sounded neutral, contemplative, and not at all seduced by the clear signs that Optimus’s frame gave to his upcoming heat. “And I would never claim to be a particularly good leader. But you have never shared a heat cycle in all the time that I’ve known you, even after we began our relationship. I don’t want you to start simply because you feel you must in these circumstances. We’ll make due one way or another, Optimus.”

Optimus’s expression softened some, a small and comforted smile tugging at his mouth.

“I appreciate your kindness, old friend. However, these circumstances _are_ such that I cannot in good conscious abandon my team for the duration of my heat. Too much could happen in four days.”

Ratchet shifted his weight from one pede to the other.

“Well, I can hardly stop you then if you’re decided.”

“Considering it would be you assisting me, you could indeed stop me if you did not wish to.”

Ratchet could only stare at Optimus in disbelief.

“And when have I ever said no to fragging you?”

And then Optimus chuckled, optics glowing as lust bled into his field.

“I believe just last week you insisted you were too busy–”

“Oh, shut up,” Ratchet grumbled. However, there was no way of hiding how Ratchet’s own optics were flaring now, or how his engine rumbled in his chassis. Ratchet had wanted to help Optimus with his heat cycles for centuries now – millennia if he was truly honest – but he had always been respectful of Optimus’s decision. And it never kept Optimus from helping Ratchet when his own heat cycles would arrive, and _Primus_ , those were good times.

Optimus’s servo reached out to cup Ratchet’s cheek, large and warm even against his burning face. The Prime’s expression was amused and his gaze heated as he took a step closer.

“In truth, it would be the other way around. I use my spike during my heat,” Optimus admitted, and Ratchet had to fight against the urge to press his thighs together to combat the throb those words invoked. Rare, but not unheard of, and it promised a long, pleasurable night. “There are many reasons I have chosen to keep my cycles to myself, even from you, Ratchet. It is only fair that I warn you before you make your decision that one of those is that my heat comes with a particularly strong desire to breed.”

“Oh.” Ratchet blinked, surprised. That was even rarer, and had only grown more so with each generation. Ratchet had never experienced such a drive himself, and would have never guessed that Optimus did so every cycle. “I certainly think I can handle a little bit of dirty talk about getting sparked up if that’s what you’ll want.”

A sudden warning popped up on Ratchet’s HUD about detecting heat pheromones, and Optimus’s optics brightened before the medic’s own as he took a bent his helm down closer to Ratchet’s.

“I will want to fill you with our child, Ratchet.”

An armor-rattling shudder went down Ratchet’s back.

“Oh frag,” Ratchet whispered, more an ex-vent than true speaking.

Optimus was close enough now that his chest bumped against Ratchet’s crossed arms. Even without his specialized systems, Ratchet would have known the air was dense with pheromones, cloying as they cycled through his vents. As if he needed any more convincing of how badly he wanted Optimus.

He had never had any real interest in carrying or having sparklings in any capacity really, but knowing Optimus did had Ratchet rapidly reconsidering.

“Obviously you may keep your reproductive systems offline, since that is not a decision I can make for you,” Optimus said plainly, as if every line of his frame and inch closer he approached wasn’t all intended to seduce Ratchet.

“Having a sparkling now _would_ be a terrible idea,” Ratchet managed, finding solace in logic when the rest of his processor was drowning in the brilliant blue of Optimus’s optics.

Optimus nearly looked sad as he nodded, his thumb stroking Ratchet’s cheek.

“Now is far from ideal.”

“And I doubt I’d be a particularly pleasant carrier.” Ratchet’s chuckle was hollow but he was fairly certain if he didn’t try to diffuse some of this tension he would choke.

And then Optimus bent his helm down until he was kissing along Ratchet’s audial, rumbling low and warmly, “Every heat cycle I have had since meeting you, I have thought of you. Not once was my heat swayed by another.” Optimus nuzzled against his helm and his free servo rested on Ratchet’s chest, above his crossed arms and atop Ratchet’s spark hidden beneath armor. “For millennia I have dreamed of seeing your spark chamber filled with our growing children.”

Ratchet’s spark swelled and his arms tightened across his chest, surprised by and concerned about the maelstrom of emotions building inside it.

“You’re fully in heat now, Optimus.”

The Prime finally paused in his pursuit to crowd Ratchet against the table and drive him mad with his voice.

“You’re correct. Your proximity sped things along I imagine,” he agreed, casual as could be, before dipping his helm down to kiss Ratchet’s neck. “Will you join me?”

Ratchet had to gather his every last bit of strength to unfold his arms and push Optimus, locking his elbows to keep the Prime held back. “Let’s move this to my room before we end up rutting right here, shall we?”

The grin that spread across Optimus’s face belonged to a younger mech – eager like a new forge and just as mischievous.

And it was catching as Ratchet easily let himself be hurried away, a similar grin tugging at his lips.

They were damned lucky it was a short trip since Optimus only held back long enough for Ratchet to make sure the door was closed and locked behind them. Before he could say a word, the Prime had him pinned against the door, shoving his thigh between Ratchet’s while capturing his lips in a searing kiss. Optimus licked into his mouth, hot and domineering, and it was with a full-frame shudder that Ratchet shifted his panels away, letting his valve slide along the strong metal pressing against it.

Ratchet could feel Optimus’s lips curl.

“You’re making it too easy for me, Ratchet,” he practically crooned against Ratchet’s lips, as if his servo wasn’t already sliding down Ratchet’s back. It only took a matter of seconds for him to grasp Ratchet’s aft in the wide span of his servo and pull his lover closer and harder against his frame.

Optimus’s spike had been released at some point and pressed insistently against Ratchet’s.

“I know better than to get between a mech in heat and his goal.” Ratchet hooked his digits into the edges of Optimus’s back plating, holding on as his frame was overwhelmed with sudden pleasure blooming where Optimus was rocking the medic’s hips, valve against thigh and spike against spike. “I’m sure you remember what happened when you last made me wait when I was in heat.”

“I think I still have the dents from how you tackled me to the ground and—how did you put it?”

Ratchet gasped when Optimus suddenly hooked his other servo under his aft as well and effortlessly lifted him until the pressure of Optimus’s frame and unmoving thigh was all that kept Ratchet up against the wall. His pedes dangled for all of a moment before he lifted them to hook around Optimus’s hips.

“Rode you like the Unmaker himself.”

Optimus groaned, his field burning where it was entrenched in Ratchet’s as he buried his face into Ratchet’s shoulder and his hips jolted, grinding against his lover’s array.

“Thinking about it get you going, hm?” Ratchet teased, as if his own hips weren’t rolling up into the pressure, his valve leaving lines of lubricant along Optimus’s thigh and hip.

“Thinking about how much I love you,” Optimus replied. Ratchet considered teasing him further – it had always amused and flattered the medic that Optimus much more often than not found his arousal in their affection for one another instead of any physical interactions. It wasn’t the first time that Optimus’s lust had been stirred up by Ratchet making some irreverent joke that had the Prime grinning.

However, before Ratchet could think of what to say, Optimus was lifting him away from the wall, nuzzling the side of his helm when Ratchet yelped and clung to him tighter.

“I can walk you know!”

“I prefer holding you,” Optimus replied as he carried Ratchet towards the berth. He caught Ratchet’s mouth in another kiss before carefully depositing the medic onto the cushioned surface. Optimus’s cooling fans roared and the naked intensity of his desire was clear as day on his face, never mind that every swirl of his field screamed his possessiveness. Ratchet shuddered, longing to have the heat-addled Prime find his release in his frame.

Optimus kissed him again while he crawled onto the berth, blanketing Ratchet as he did, pinning the medic down with the pressure of his servos and the weight of his hips. Ratchet’s array pulsed with need as he felt the Prime’s spike slide and drag along his hips.

“I hope our child will have your humor,” Optimus murmured against his lips as his hips tilted back, allowing his spike to settle against Ratchet’s valve. “Though any way in which they take after you will be perfect.”

“ _Primus,_ Optimus.” Ratchet was truly trapped between the berth and Optimus’s frame, only able to tighten his legs around Optimus’s hips and moan as the Prime’s spike pressed inside in one long push. It pulsed inside him, unyielding to the clenching of his calipers as Ratchet was awash with bliss. Optimus’s engine rumbled as he ex-vented harshly, a soft, low sound of pleasure escaping him when he bottomed out. “I’m not – _oh frag_ – I’m not even carrying yet, and you’re–”

The statement was lost as Optimus pulled back and quickly snapped his hips forward with enough strength that the medic would have been pushed up the berth were he not pinned by Optimus’s servos. Ratchet threw his helm back with a shout, his own servos scrambling to wrap around Optimus’s shoulders and neck, holding on for dear life as his lover pounded into him with an intensity normally saved for the end of their love-making.

Ratchet’s frame burned with need as his valve throbbed under the circuit-frying abuse.

“Say it again,” Optimus asked, his voice deep and already hinting at gruffness that had Ratchet clenching around his spike and his digits digging under Optimus’s plating.

“S-say what?”

Optimus’s optics burned as he stared down at Ratchet as if he were the greatest gift imaginable.

“That you’re not carrying _yet_.”

Ratchet trembled and gasped a moan as Optimus’s spike hit the back of his valve over and over. Never, in the millennia of their friendship and eventual bond, had he ever considered that this would be something Optimus would want from him, let alone desire with such intensity. There was his heat cycle powering it, yes, but the stark honesty at the forefront had Ratchet’s spark swelling, nearly feeling as if it was choking him with affection and a desire he had never felt before, let alone so _strongly_.

“Not yet—haah, frag, _frag_. B-but at this rate, it won’t be long.”

Optimus’s engine revved hard in his chassis and Ratchet offlined his optics with a drawn out groan as a wave of his lover’s pleasure washed over him and heightened his own, overwhelming and nearly sending him into overload already.

It only took a couple seconds to find the long untouched coding that cycled open the barrier between his valve channel and his forge. Without onlining the connector to his spark, there was no danger of sparking, and if Ratchet could drive his lover wild knowing his transfluid would spill into his forge?

It would be well worth the cleanup later.

“Come on,” Ratchet managed between grunts, tightening his legs around Optimus’s hips, his pedes scraping the back of the Prime’s thighs. “Come on, Optimus—fill me up, spark me up, come on!”

Optimus’s servo shoved Ratchet back against the berth while the other grasped him by the hip and yanked while thrusting, nearly doubling the medic over as the Prime panted out a curse, face pinched with desperation as he trembled and finally broke. His engine roared when Optimus overloaded, hips pressed flush against Ratchet’s even as he jerked, the servo on Ratchet’s hip moving him with each movement.

The waves of transfluid as they spilled into Ratchet’s forge had his optics flaring and his voicebox glitching. He had never used the organ, known it only insofar as he needed to know his frame functioned normally, had not even considered how novel the sensation would be. Feeling Optimus inside him in a way no other mech had been, actually filling him instead of overflowing over his valve lips, each roll of Optimus’s hips pushing more liquid heat inside–

Ratchet cried out as he was catapulted into his own overload, his grasping servos scraping paint from Optimus’s arm and shoulder. His valve convulsed and squeezed, milking Optimus for his release and sending aftershocks of ecstasy through his sensornet with every drop that slipped into his forge.

Barely seconds had passed for Ratchet to even try to drag cool air into his boiling frame before his interface protocols dialed up again. Optimus’s digits were dragging along his valve where sensor-laden mesh stretched around the girth of his Prime’s spike and a shaky, tank-deep noise escaped Ratchet’s lips.

Attempting to arch up led him nowhere as Optimus’s servo against his shoulder held him firm against the berth.

“Did you open your forge?” Optimus asked, quiet and oh could Ratchet hear the awe behind the question. He didn’t even need to check to know there was only lubricant slicking their joining, that the lack of transfluid squeezing out around his spike would make Optimus suspicious, and _Primus_ , Optimus’s still fully pressurized spike throbbed inside him, promising so much more.

Ratchet’s optics flickered online and he grinned impishly up at his lover.

“Where else would your transfluid have gone?“

Optimus was on him in an instant, kissing him dizzy while his field surged with love and heat.

“You’re so good to me,” Optimus praised, cupping Ratchet’s helm as he kissed his lips, his cheeks, whatever his mouth could reach. His hips were already moving again, rutting into Ratchet to drag his spike along nodes now over-sensitized in the wake of Ratchet’s overload. When Ratchet let a gasping whine escape, Optimus simply nuzzled into the nook of his shoulder and kissed his neck cording. “Feel so good, so perfect around me. I want to fill you completely.”

“W-well, you’re off to a good start,” Ratchet said, chuckling warmly as afterglow was quickly shifting into round two. Primus only knew how many rounds there would be before finally the heat abated. Ratchet pulled Optimus’s helm up to kiss him again, biting down on his bottom lip and tugging just to feel his lover’s hips jerk and snap flush against his valve before releasing him. “I know your heat isn’t over yet so don’t hold back.”

“Very well, Ratchet.”

Instead of returning to his punishing pounding from before, though, Optimus continued to just roll his hips, grinding into Ratchet, leaving him full with the Prime’s spike while his housing rubbed against Ratchet’s anterior node.

Optimus’s chest clicked and Ratchet’s optics went wide as the heat of the Prime’s spark cascaded across his own chest.

And Optimus’s lips were curled into a playful smile.

“Give me your spark so I can truly fill you completely.”

They had merged while interfacing before – Ratchet knew that, knew the feeling of Optimus’s spike inside him while his spark was completely submerged and entwined with his love’s. But the slight shifting of liquid inside his forge had the medic choking back a whine as his hips quivered and his armor shifted away to reveal his spark.

Optimus did not hesitate, bending to kiss Ratchet deeply and letting his spark reach out.

 _Primus_.

The Prime’s entire being, down to his very spark, was so completely focused on Ratchet. On having him, holding him and fragging him and _filling_ him, on joining with him so completely that their very sparks would splinter and their shards become permanently intertwined to grow into a new soul.

On loving Ratchet so fiercely that life could be forged from their bond.

Optimus’s heat hit next soon after, overwhelming in its need to chase that desire to its conclusion.

Ratchet’s helm snapped back as he cried out.

His spark echoed its mate’s song as they merged.

Without another thought the connection between his spark chamber and his forge lit up, and with it the organ hummed to life. It was completely hidden under the powerful whirling of their cooling fans, the clanging and grinding of their frames, Ratchet’s litany of cursing and moaning. But still, Optimus’s helm snapped up and his optics blazed as stared down at Ratchet, his frame suddenly going still as his mouth hung open.

“Ratchet–”

“Like my bucket of bolts is even capable of sparking anymore,” Ratchet interrupted, hoping his self-deprecation could stave off discussion. As if Optimus couldn’t feel the trepidation in his spark, or the way it soared despite it with never considered possibilities, or the small flicker of hope.

At the very least, Optimus’s frame heeded the desperate clenching of Ratchet’s valve, picking up the pace as he thrust into Ratchet.

Optimus’s kiss belied the pounding of his hips, soft and pleading.

“Are you certain?”

“There’s no guarantee that anything will come of this–”

“ _Ratchet_.”

Everything else was gone – all Ratchet’s worries and fears, their companions, their _war_ – because all that Ratchet could comprehend was his lover’s frame and spark where they intertwined with his own.

“Yes.”

Optimus wrapped his arms around Ratchet, one under his shoulders to keep this chests close and their mouths pressed together while the other hooked under his hips, lifting them to better angle his thrusts to hit Ratchet’s ceiling node each and every time. The frantic pace had returned as Optimus’s vents blasted heat and Ratchet panted between grunts.

“Then I will take all night if that’s what it takes,” Optimus murmured into their kiss, his spark twisting tight around Ratchet’s and sharing his own pleasure to add to his lover’s euphoria. “Until you’re overflowing and have lost count of your own overloads. By morning you will be carrying our child, Ratchet. I can promise you that.”

Ratchet could only hold onto Optimus all the tighter as pleasure and love overwhelmed him and he dragged his lover into another overload with him.

* * *

“Are you alright?”

Ratchet hummed as he finished booting up from his recharge. He didn’t bother to move though, far too comfortable laying against and half across Optimus, perfectly settled in the nook of his arm while his legs sprawled across the Prime’s hips and thighs.

“More than,” he purred, a soft chuckle escaping him after. “Though if you mean my frame, well, I don’t think I’ll be able to walk straight for a few days at least.”

“I’d apologize if I didn’t know how much you enjoyed yourself.” Optimus servo was soothing where it stroked his lower back, and the other that Ratchet had interlaced with one of his own squeezed for a moment. “Though there are other things I probably should apologize for.”

“It’s fine. You could have told me sooner though.”

“I didn’t see much point in bringing up the topic,” Optimus admitted. Ratchet onlined his optics and turned his helm just enough to look up at him. Something sad flickered across the Prime’s face. “At least not until we could truly consider raising children. Considering our positions and all that has happened, that time never came to be.”

The Prime was covered with paint transfers, long strips of white and orange across his armor. There was no doubt that Ratchet had faired just as poorly. Ratchet pressed a soft kiss against the mark under his cheek.

“It’s fine, Optimus. Really.”

Optimus’s hold on Ratchet’s servo tightened.

“I hope you know that if something comes of this, you should not feel obliged to keep–”

“I’ll keep it,” Ratchet interrupted. When Optimus looked at him with surprise clearly etched across his face, the medic shrugged and finally managed to shift so he could look at Optimus better. The movement awoke every ache in his body, and the sloshing in his forge had him wincing. He waved off Optimus’s look of concern though.

“Look. No, deciding this while you were in heat and I was caught up in it wasn’t a great idea. And no, having a child in the middle of this damned war isn’t particularly responsible. And you’ll have to put in a lot of work because frankly, I’ve never been good with sparklings, let alone know how to raise one beyond maintaining their physical health. And by the Allspark, the whole team is going to regret this decision for me since there’s no way I’ll find protoform material in this corner of the universe, so I’m going to have to actually use my forge to make it myself, so I will make for awful, _miserable_ company.”

“But?” Optimus prompted, smiling a bit now and unable to hide the subtle stirrings of hope in his field.

Ratchet ex-vented tiredly as he shrugged.

“But it would be ours, so obviously I’ll keep it.”

Optimus’s engine purred softly under Ratchet.

“ _Are_ you carrying?”

“No way of knowing for at least a week,” Ratchet replied clinically.

“I’ve heard before of mecha who say they knew the moment they sparked.”

“A bunch of make-believe. A new spark is small enough that it’s undetectable in the carrier’s spark until it grows. A scanner will notice it long before I’ll feel it.”

Optimus lifted their joined servos so he could kiss Ratchet’s knuckles.

“Romantic as always, old friend.”

“Should have considered that before deciding I was the mech you wanted to spark up.”

“Obviously I’ll have to carry with the next one,” Optimus replied with clear amusement.

Ratchet managed a short rev of his tired engine as he purred, “I wouldn’t even need to be in heat to gladly assist you with that.”

Optimus chuckled and his field was warm and happy where it melted with Ratchet’s.

“I must admit, I _quite_ enjoyed putting that sparkling in you.”

“You and I both, Optimus.”


End file.
